There have been significant strides in surgical navigation systems in recent years. The current systems provide visualization of a surgical site on a computer monitor. Conventional systems operate by first creating a high-resolution three dimensional image of the anatomical region of interest. In dentistry, the preferred imaging modality is cone beam computed tomography, referred to herein as the “CT.”
Using the image of the anatomical region, the surgeon creates a pre-operative plan in the area of operation identifying the desired location, depth and orientation of an implant on the CT image.
During the operative procedure, a software system including tracking software, aligns or adjusts the position of the patient's jaw as observed in the operating suite with the pre-operative plan that is stored on the computer system. The system then detects the surgical tool (drill) and determines the location and orientation of the surgical tool with respect to the patient and the pre-operative plan. This information is then depicted on the screen as a representation.
Using this information, in order to place an implant in a jaw, the surgeon will follow these steps:
Find the position in the patient's jaw where the hole should be drilled into the bone.
Place the drill tip in the proper position at the desired location, rotate the drill about the tip to the position the drill at the correct angular orientation.
Drill into the tooth or bone, counteracting the drill's tendency to deviate from the desired trajectory as the bit twists into the bone.
Continue along the planned trajectory until the drill tip is at the pre-planned depth within the bone.
Failure to appropriately place the implant in the pre-planned location can result in a suboptimal aesthetic outcome or may injure the patient if the implant impinges on a nerve or erupts into surrounding anatomy if driven too deeply or in the wrong location.
Because the surgeon is concerned with correct placement in three dimensions, most state of the art navigation systems simultaneously depict the instantaneous location of the surgical instrument with respect to the patient's anatomy from several different viewpoints. Referring to FIG. 1, a display from conventional navigation systems is shown. The display 10 includes a panoramic view 10, typically of the entire jaw or at least the upper or lower jaw portion captured in an earlier scan. On the panoramic the current position of the drill 11 is represented as well as the depiction of the planned implant 12. A live camera view 13 of the operating suite may be included. A computer generated comparative view 14 is displayed visually depicting the current displacement in buccal/lingual and mesial/distal directions of the drill 11 with respect to the planned implant 12. A computer generated comparative view 15 is displayed visually depicting the current displacement of the angular orientation of the drill 11 with respect to the planned implant 12 along its long axis.
FIG. 1 also includes a front view 16 and a side view 17 of the prior CT scans with the planned implant 12 and the current drill tip location 11 illustrated. These views also include a depiction of a nerve 18 in close proximity. The long axis 19 of the planned implant is illustrated depicting the positional misalignment in each plane. These views permit the surgeon to see a visual depiction of the current depth of the drill tip 11.
While conventional systems provide a combination of images that unambiguously show the orientation, depth and trajectory of a surgical instrument inside the patient with respect to a planned implant location, the multiple views that the surgeon must constantly comprehend can be exhausting to the surgeon. The surgeon must constantly shift focus between the different views, ensuring that every movement made to correct a deviation in one view does not adversely introduce error that can only be detected in a different view. These shifts in focus lead to user strain and can potentially lead to suboptimal outcomes.
A need exists for an improved guidance system that depicts in real time the position and orientation of the surgical tool with respect to the patient's body and the planned implant trajectory. As a hole is drilled for the implant or as the implant is delivered into the bone, the system should clearly indicate if the surgeon is deviating from the planned trajectory in such a manner as to allow for straightforward correction. Additionally, upon the drill reaching the planned location within the body, the event should be readily apparent to the surgeon so further drilling can be stopped. The surgeon is trying to continuously maintain a proper position in the jaw with alignment to the planned trajectory all while drilling to the correct depth. It is therefore desirable that all the pertinent information is presented in a manner appropriate for simultaneous consumption by the surgeon. The current state of the art navigation systems fail to meet these basic objectives.